The present invention relates firstly to NC complex automatic lathes for carrying out machining using a plurality of tools.
The present invention relates secondly to NC complex automatic lathes for carrying out front machining of a workpiece (hereinafter, referred to as "main machining") and rear machining thereof using a plurality of tools.
The present invention relates thirdly to NC automatic lathes constructed such that a plurality of tool slide members having bits around a workpiece are driven by a servo motor to undergo respective displacements to effect cutting operation of the workpiece.
Conventionally, from the first point of view, there are two types of NC automatic lathes provided with a plurality of radially arranged tool slide members (hereinafter, referred to as collectively "comb type tool slide"), or a turret type tool slide. The Comb type tool slide is designed such that a plurality of tools are disposed around a workpiece and one or more of them is selectively displaced with respect to a rotating workpiece to effect machining thereof. This type of tool slide has good machining accuracy since it does not need indexing rotation for selection of tools. Normally, a bit piece is attached as a tool for suitably effecting accurate machining such as finishing work.
On the other hand, the turret type tool slide is constructed such that one tool is selected from a plurality of tools attached to indexed positions, and the indexing rotation is carried out to place the selected one in a given working position to thereby displace the selected tool to effect machining of a workpiece. This type of tool slide is advantageous in that a multiple number of tools can be mounted to carry out secondary machining such as drilling work by a rotary tool, e.g., drill-end-mill, and grinding work.
With regard to the automatic lathe provided with a comb type tool slide, since there is no need to carry out indexing rotation for selecting a tool as described before, such type of the lathe has advantages such as short cycle time for selections of tools and good cutting accuracy. However, it has drawbacks such as deficiency of tools due to its limited number of available tools and limited kinds of possible machining modes.
On the other hand, the automatic lathe provided with a turret type tool slide features that a multiple number of tools can be mounted. However, there are various drawbacks such as bad machining accuracy and long selecting time of tools due to indexing rotation for selection of tools, as compared to the comb type tool slide.
Conventionally, from the second point of view, the NC complex automatic lathe carries out the main and rear machinings of a workpiece by various methods, for example, as shown in FIGS. 10A and 10B. Namely, according to the first method shown in FIG. 10A, a main spindle base 81 rotates a main spindle which chucks a workpiece, while the main spindle base 81 slides in a direction Z1. When carrying out the main machining, a pair of tool slides 82 and 83 which constitute a comb type tool slide are driven to slide in directions X1 and X2, respectively. On the other hand, when carrying out the rear machining, immediately before cutting off the workpiece chucked to the main spindle a back-main spindle base 84 moves to a direction Z2 to receive the workpiece in a back-main spindle. Then, the back-main spindle base 84 moves transversely in a direction X3, so that the workpiece is subjected to the rear machining by a fixed tool slide 85 which is provided with a tool for use in the rear machining.
According to the second method shown in FIG. 10B, there is provided a main spindle base 91 driven in a manner similar to the FIG. 10A case. When effecting the main machining, a pair of turret tool slides 92, 93 are driven in direction X1 and X2, respectively. On the other hand, when effecting the rear machining, in manner similar to the first case, a back-main spindle base 94 is driven in a direction Z2 toward the main spindle base 91 such that a back-main spindle receives the workpiece. In this position, the rear or back machining is carried out by a rear machining tool which is attached to either of the turret tool slides 92 and 93.
However, in the first conventional method, since the main machining is carried out solely by the comb type tool slide, there are caused drawbacks such as deficiency of tools due to a limited number thereof and relatively small freedom of the machining, although the first method has some merits such as relatively short cycle time of tool selection and relatively good cutting accuracy.
With regard to the second conventional method, while a pair of turret tool slides are utilized to increase the number of tools, there are caused drawbacks such as relatively long tool selection time and relatively bad tool setting accuracy because of indexing rotation for tool selection, as compared to the comb type tool slide.
Particularly when carrying out the rear machining such as rear drilling of a workpiece chucked to the back-main shaft by means of the turret tool slide, there would be caused the drawback of degradation of machining accuracy such as center deviation in drilling and correction failure of bit, due to indexing error of the turret and positional error of tools attached to the turret tool slide.
Conventionally, from the third point of view, there are known several methods for cutting a workpiece by driving a plurality of tool slides in the NC automatic lathe. According to a first method as shown in FIG. 18, a signal servo motor M is utilized to drive each of five tool slide members 101a-101e. Namely, one of the tool slide members 101a-101e is selected together with one of the corresponding cylinders 102a-102e, and the selected cylinder and the corresponding tool slide member are driven by the servo motor M through a corresponding one of the corresponding cylinders 102a-102e, and the selected clyinder and the corresponding tool slide member are driven by the servo motor M through a corresponding one of levers 103a-103e.
On the other hand, according to a second method as shown in FIG. 19, three servo motors M1, M2 and M3 are utilized to drive five tool slide members 105a-105e. Namely, the first servo motor M1 is adapted to drive directly only the tool slide member 105e. The second servo motor M2 is adapted to alternatively drive the tool slide members 5c and 5d back and forth through a lever 106. The third servo motor M3 is adapted to alternatively displace a pair of tool slide members 5a and 5b disposed on a common slider 107 in opposed relation to each other with respect to a workpiece .omega.. By such construction, three tool slides are selectively driven so that three bits can concurrently contact with the workpiece .omega. to carry out concurrent cutting.
However, in the first method mentioned above, as shown in FIG. 18, one tool slide member is selectively driven among the tool slide members 101a-101e, thereby causing the drawback that concurrent cutting work could not be effected by simultaneously driving a plurality of tool slide members 101a-101e to operate a plurality of bits.
On the other hand, in the second method, as shown in FIG. 19, the three servo motors M1, M2 and M3 can be operated to drive, for example, each of the tool slide members 105a-105e in directions indicated by the arrows to carry out concurrent cutting work by the selected three tool slide members 105a, 105d and 105e. However, the pair of tool slide members 105a and 105b are fixed on the common slider 107 opposite sides with respect to the workpiece .omega.. The opposite tool slide members 105a and 105b are alternatively advanced to the workpiece .omega. by back and forth displacement of the slider 107. Therefore, the pair of bite of the opposite tool slide members could not carry our concurrent cutting work, i.e., perfect balance cutting work. In addition, the increased number of the servo motors may disadvantageously boost a production cost of the lathe.